Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
  • C22B7/001—Dry processes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/248—Binding; Briquetting ; Granulating of metal scrap or alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B19/00—Obtaining zinc or zinc oxide
  • C22B19/30—Obtaining zinc or zinc oxide from metallic residues or scraps
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• the invention relates to a method for removing zinc from phosphating sludge at elevated temperatures and under reducing conditions and in the presence of additives, and to its use within the rolling process for working up residual smelting from a metallurgical plant.
• Phosphating with zinc phosphate solution is a widely used process in the metalworking industry.
• the phosphate layers produced on metals by this process serve in particular to facilitate sliding and non-cutting cold forming, as well as for corrosion protection and as a lacquer primer.
• a phosphating sludge is formed in addition to the desired conversion layer, which must be removed regularly from the treatment baths.
• the dried sludge from the treatment of steel and iron has the following composition: 2 - 20% Zn; 10-30% Fe; 30-45% P2O5. If zinc surfaces are phosphated, the Zn content in the sludge is approximately 38-45%.
• small amounts of Na, Mn, Ni, Ca, Cu, Co and other cations may also be present.
• the anions NO3 ⁇ , Cl ⁇ and F ⁇ can also be contained in small amounts.
• the object of the invention is to provide a method by which the valuable substances contained in the phosphating sludge phosphorus and zinc are converted into reusable form, which works wastewater-free and in particular is simple to carry out.
• the phosphating sludge is mixed with additives which are capable of forming slag-like (solid, non-volatile) iron, calcium and / or barium compounds with the phosphorus component of the phosphating sludge at elevated temperature implements at least 800 ° C.
• the Fe-P compounds have the property of rearranging into lower-P compounds with increasing temperature and releasing phosphorus. To put it simply, it can be represented as follows (temperature rises in the direction of the arrow): FePO4 ⁇ FeP ⁇ Fe2P ⁇ Fe3P In most cases, there are mixtures of two compounds. Fe2P does not give off phosphorus when heated. The formation of Fe3P takes place only if there is a sufficient Fe supply.
• a graphic can be made from these values and the corresponding mixing ratio can be read for each desired Fe excess. It follows, for example, that a mixture of 18% phosphating sludge (1.8 t) and 82% dust (8.2 t) must be set for a desired Fe excess of 100% according to the above example.
• the phosphating sludge is reacted to form iron compounds at a reaction temperature of at least 900 ° C. It is even more favorable to carry out the reaction at at least 1000 ° C., in particular at at least 1100 ° C.
• the reaction rate increases with increasing temperature, so that - based on an existing system - the achievable throughput also increases.
• a further advantageous embodiment of the invention provides for an Fe / P molar ratio of 1.0 at a reaction temperature when iron compounds are added and thus slag-like iron compounds are formed with the phosphorus component of the phosphating sludge from ⁇ 950 ° C, from 1.5 at a reaction temperature of 950 to 1050 ° C and from 2.0 at a reaction temperature of ⁇ 1050 ° C. adjust.
• the phosphating sludges are advantageously reacted with highly iron-containing oxidic iron compounds.
• Suitable iron compounds are, for example, oxidic iron ores, iron oxides such as those e.g. in pyrite roasting or regeneration of hydrochloric or sulfuric acid pickling agents.
• the implementation can also be carried out using mill scale or scrap.
• a particularly preferred embodiment of the invention consists in converting the phosphating sludge with metallurgical dusts to form slag-like iron compounds. Dusts of this type are particularly suitable because, on the one hand, they occur in sufficiently large quantities and, on the other hand, contain zinc as the main constituent in addition to iron, which is then volatilized together with the zinc content of the phosphating sludge.
• Another, likewise advantageous embodiment consists of reacting the phosphating sludges to form Ca and / or barium compounds with additives containing Ca or Ba in accordance with a molar ratio Ca: P or Ba: P ⁇ 1.5.
• the above-mentioned molar ratio only applies exactly when the phosphating sludge to be processed does not contain iron, which primarily slags phosphorus. If iron is also contained in the phosphating sludge, the molar ratio of Ca: P or Ba: P can be reduced in accordance with the above-mentioned and temperature-dependent binding capacity of iron to phosphorus.
• a further expedient embodiment of the method according to the invention consists in compacting the mixed phosphating sludge / additives into pellets, briquettes or similar agglomerates.
• easier handling of the starting materials and more precise dosing can thus be achieved.
• the dust discharge from the exhaust gases is largely reduced, so that the result is a purer zinc product.
• solid fuels are coal, coke, coke breeze and the like.
• the use of the method according to the invention has the advantage that there is no waste water which would have to be cleaned additionally.
• the procedure is also simple.
• the phosphating sludge and the aggregates can already be mixed in the storage bunkers.
• the phosphating sludge should contain so little residual moisture that it is free-flowing, otherwise, if the residual moisture is too high, their thixotropic behavior would make dosing more difficult. It is not necessary to neutralize the sludge at the place of accumulation.
• continuous or discontinuous loading is possible from the storage bunkers.
• the residual moisture in the phosphating sludge can be driven off in the reaction unit. An additional unit is not required.
• the actual reaction is quantitative above 800 ° C. If the atmosphere in the gas space of the reaction unit is also reducing, the elemental zinc is volatilized. In an oxidizing atmosphere in the gas space, the zinc escapes in the form of zinc oxide.
• the exhaust gases can be cleaned in accordance with the prior art, so that the volatilized zinc or zinc oxide can be reused and no pollutants get into the environment.
• the tests were carried out in a tube furnace.
• the sample was placed on a boat in the oven and left there under a reducing atmosphere for 2 hours at the respectively set temperature.
• a Fe: P molar ratio of 1.0 is sufficient for practically complete P integration, and a molar ratio of 2.0 is required at higher temperatures. It is also striking that at 900 ° C the dezincification increases with an increasing amount of Fe. The dezincification is also determined at 1000 ° C. by the Fe: P molar ratio, so that an Fe: P molar ratio of ⁇ 2.0 should be set if complete Zn volatilization is also to be achieved in addition to complete P incorporation.
• the resulting residues are Fe-P alloys and can be used in the steel industry. They can be stored outdoors.
• the Fe-P compounds formed are stable even at relatively high temperatures of up to 1300 ° C, as can occur, for example, in the rolling process, and no P is evaporated at a sufficiently high Fe: P molar ratio.
• the Ca shown in Table 3 can therefore be replaced in whole or in part in a molar ratio by Ba.
• the phosphating sludge used contained an intrinsic Fe content corresponding to an Fe: P molar ratio of 0.5, and also small amounts of Na and Mg.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Organic Chemistry (AREA)
• Geology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Processing Of Solid Wastes (AREA)
• Treatment Of Sludge (AREA)

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Publications (2)

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Citations (6)

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• 1991
  • 1991-05-30 DE DE19914117716 patent/DE4117716A1/de not_active Withdrawn
• 1992
  • 1992-01-08 US US07/818,011 patent/US5198020A/en not_active Expired - Fee Related
  • 1992-05-06 DE DE59204558T patent/DE59204558D1/de not_active Expired - Fee Related
  • 1992-05-06 ES ES92201280T patent/ES2083066T3/es not_active Expired - Lifetime
  • 1992-05-06 EP EP19920201280 patent/EP0520524B1/fr not_active Expired - Lifetime

Patent Citations (6)

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